Even if you take the clues and make the chassis on your own, it will cost you less.

Not in the US or Canada, it won't. The extruded heatsink material is particularly difficult to source in low volumes, since it tends to be stocked and bulk-sold in lengthy sections. There aren't many places that can do custom machining and anodizing of this quality and the labor rates are going to be pricey. I'm seeing easily $500/unit in materials and labor for a low-volume run, and that's assuming they have CNC equipment and you provide them with compatible AutoCAD files, and that buys you a box of pieces, not a chassis -- you would still have to assemble it.

Those case are $150 to $250 from specialty retailers. (Thanks Bauxite)Some people pay $40 for an after market heatsink+fan, those case come with a passive cooling solution.So the price is not extravagant for what look like some solid all metal construction + cooling.

I think the case have a clean look, to each his own, but most importantly they have a passive cooling design, using the case side fins.So zero moving parts, zero noise. and with a modern platform, it will sit at ~20watt idle. (even so my HTPC is in sleep mode 18+ hours a day, unless its Olympics time)

I have been using a HTPC exclusively since 2002, and in the past 10 years this is so far my favorite HTPC case design.And with the A10, it seem like a perfect combination.

AMD indicated that they will still produce FM2 APU in 2015, so this should be a long lasting HTPC... if you choose to use Trinity guts.